1. Field of the Invention
The present invention provides a downhole adjustable bent housing for use in directional drilling of wells used to recover oil and gas, and a method for directionally drilling a well to recover oil and gas.
2. Background of the Related Art
Wells are generally drilled to recover natural deposits of hydrocarbons and other desirable, naturally occurring materials trapped in geological formations in the earth's crust. A slender well is drilled into the ground and directed to the targeted geological location from a drilling rig at the surface. In conventional “rotary drilling” operations, the drilling rig rotates a drillstring comprised of tubular joints of drill pipe connected together to turn a bottom hole assembly (BHA) and a drill bit that are connected to the lower end of the drillstring. The BHA typically comprises a number of downhole tools including adjustable bent housings, drill collars and mud motors, and is generally within 30 feet of the drill bit at the end of the drillstring. During drilling operations, a drilling fluid, commonly referred to as drilling mud, is pumped down the interior of the drillpipe, through the BHA and the drill bit, and back to the surface in the annulus around the drillpipe. Mud motors are often used to rotate the drill bit without rotation of the drillstring. Pressurized mud pumped down the interior of the drillstring is used to power the mud motor that is mechanically coupled to and turns the nearby drill bit. Mud motors offer increased flexibility for directional drilling because they can be used with stabilizers or bent subs which impart an angular deviation to the BHA in order to deviate the well from its previous path and in the desired direction.
Surface adjustable bent housings are downhole tools that make up part of the BHA and are typically connected either between the mud motor and the drill bit or above the mud motor and the drill bit. Such bent housings are designed to provide an annular deviation in the BHA to directionally orient drilling action at the drill bit. A surface adjustable bent housing may be adjusted to a particular setting by tripping the drillstring and setting the bent housing to impart a desired angular deviation to the well.
A downhole adjustable bent housing offers savings in rig time and well costs because it is adjustable without being removed from the well. A downhole adjustable bent housing that is positionable, or deployable, from the surface can be used to efficiently influence the drop or build angle of the boring direction of the drill bit. The angle of attack of the drill bit and the resulting direction of the well can be guided using the downhole adjustable bent housing.
It is well known in the drilling industry how to obtain reliable three-dimensional location data for the bottom of the well being drilled. The driller compares this information with the target bottom hole location to determine needed adjustments in the path of the well, and the adjustments to the direction of drilling of the well may be made using the present invention.
Prior art surface adjustable bent housings use a complicated series of three connected housings that rotate independently to provide varying configurations from aligned to bent relative to the BHA. These tools require complex schemes for controlling rotational positions of each housing.
It is therefore an object of the present invention to provide a downhole adjustable bent housing that can be easily and repeatedly deployed or retracted by controllable changes made at the surface in hydraulic mud pressure in the drillstring.
It is a further object of the present invention to provide a downhole adjustable bent housing that can be adjusted without the use of wired or cabled control systems that complicate drilling operations, and that is reliable and simple to deploy and retract.
It is a further object of the present invention to provide a downhole adjustable bent housing that, once locked into its deployed position, allows the driller freedom to change the rate of the mud pumps without affecting the deployed condition of the tool.
It is a further object of the present invention to provide a downhole adjustable bent housing that provides the driller with reliable detection of the deployed or retracted status of the tool.